Constructing Built-in Hydroxyl Relay Through Ru/RuO₂ Interfaces for Efficient PEM Water Electrolysis

As promising non-iridium alternatives, RuO₂-based catalysts demonstrate superior acidic oxygen evolution reaction (OER) activity, however, their poor stability in acidic electrolyte remains a critical bottleneck hindering their application in proton exchange membrane water electrolysis (PEMWE). Herein, we construct a RuO₂-based catalyst modified with Ru nanoparticles and grain boundaries (mG-RuO₂) to simultaneously improve OER activity and stability. The resulting mG-RuO₂ catalyst demonstrates superior acidic OER performance, requiring only 171 mV overpotential to reach 10 mA cm^-2 and showing stable operation over 650 h. Theoretical calculations combined with in situ spectral analysis reveal that Ru nanoparticles not only break the H-bond network of water in the double-layer structure but also overcome the limitations of the adsorbate evolution mechanism pathway through efficient OH* spillover, thereby simultaneously enhancing the activity and stability of mG-RuO₂. Moreover, the grain boundaries increase oxygen vacancies in RuO₂, thereby suppressing the lattice oxygen mechanism and improving structural stability. More importantly, mG-RuO₂ requires only 1.556 V to reach 1 A cm^-2, while maintaining outstanding stability for over 500 h under this condition. This work elucidates the special OH* spillover mechanism in acidic OER, shedding light on the rational design of highly active, and stable RuO₂-based electrocatalysts for PEMWE.